The organic ion metabolites of the fluorocarbon tetrafluoroethylene: tetrafluoro- ethylglutathione (TFEG), tetraethylcysteine (TFEC), N-acetyl tetraethylcysteine (NA-TFEC) and their analogues have been shown to be nephrotoxic, targeting renal proximal tubules in both animals and humans. However, the actual mechanisms by which these agents cross cell membranes remain poorly understood. The primary objective of this proposal is to understand the transport mechanisms by which selected nephrotoxicants enter the renal cell and the ramifications on renal cell function and cell injury. Specifically, the transepithelial secretion of glutathione conjugates, and the transport of cysteine and NA-cysteine conjugates by an amino acid and the organic anion pathway, respectively, have been implicated in their accumulation and toxicity to the renal proximal tubule. Experimental data show that more than one carrier-mediated transport pathway is involved in the movement of structurally related cysteine conjugates across the luminal and basolateral membranes of the renal cell. To this end, this proposal will address the following hypotheses: 1a) Both peritubular and luminal transport pathways are qualitatively and quantitatively important in the accumulation of the cysteine and N-acetyl cysteine conjugate metabolites of tetra- fluoroethylene by renal proximal tubule cells, 1b) The transepithelial secretion of the glutathione conjugate of tetrafluoroethylene (TFEG) provides an additional route by which this metabolite is transported to the luminal membrane to subsequently produce toxicity to renal cells, and 2) Manipulation of these various transport pathways can influence the onset and degree of toxicity produced by these agents. Primary cultures of rabbit renal proximal tubule cells grown on plastic and/or membrane supports, and rabbit renal proximal tubule suspensions will be used to examine the luminal and basolateral transport processes involved in nephrotoxicant accumulation and how their transport influences toxicity. Ultimately, these studies will better link the importance of nephrotoxicant transport to their potential toxicity and lay the ground work for therapeutic approaches to protect against nephrotoxicity.